Answering Your Questions
World Mechanics:
Q: Regarding the leveling and class system, when do people unlock their third class?
A: Because of the nature of experience and classes, it's not uncommon for the primary and secondary class to grow at different rates depending on how you're earning your experience, so it's whenever the total of both classes hit 60.
Q: Do all classes go through evolution? When do they go through evolutions? Since Zaren has a mythic class already, does that class not evolve?
A: Class evolutions occur when the class hits 25/50/75/100. Most often the evolutions are somewhat linear, and more common classes can have evolutions as simple as Swordsman -> Swordsman II though the heroes of the story get the benefit of more interesting classes because plot. There are classes that can't earned at level one, even for mythic classes, so Zaren will be facing a class evolution of his own in the near future...
Q: How do people determine the rarity of classes?
A: There are certain artifacts out there capable of analyzing class rarities, and while forcing classes is frowned upon there is documentation of most classes rare and below. It's easier to spot mythic, unique, and legendary class skills because they have epigraphs (the flavor text in italics) and are more powerful, but artifacts are the only surefire way to know the rarity of a class itself.
Q: Paraphrased: questions about Noelle's race, the Malachai and the demi-human races:
A: Noelle is technically not a beastkin. Currently (I don't plan to add more, but who knows if inspiration will strike me) there are nine different divisions of demi-human, each with three races that share a common ancestor. I'll put a list in a spoiler so it doesn't take up too much space.
Celestial: Arelim, Seraphim, Nephilim
Infernal: Tiefling, Erinyes, Oni
Beastkin: Nekomata, Kitusne, Lycanine
Elf: Dark, Wood, High
Dwarf: Mountain, Hill, Deep
Draconic: Dragonling, Drakken, Half-Dragon
Fae: Nymph, Nereid, Seelie
Siphon: Succubus/Incubus, Vampire, Siren
???: Malachai, ???, ???
Misc. Questions:
Q: How long do you envision this the series?
A: It's hard to say. I certainly didn't think the journey to the capital was going to take as long as it has, but It's the first of three major "arcs" that I have in my head, though a lot of the nuances of those arcs are still in the air. I don't have a solid answer to your question other than to say where we are right now is probably somewhere between a quarter and a third of what I have planned overall, though that's subject to change as I write.
Q: Where are the characters relative to one another?
A: Zaren started in the north and is currently heading south towards the capital, which is about a week away as of last chapter (assuming nothing else hampers their progress, of course). Allie's first chapter, though unstated, took place a couple days to the west of the capital, and her last mission took place south of the capital by a few days, though she returned to the capital at the end of her chapter.
Q: Will the plot transition to some kind of Kingdom Building once Zaren arrives at the Capital?
A: It won't quite be kingdom building, but there will definitely be some emphasis on Zaren building up his household and resources. It will definitely be a shift in tone from them being on the road up until this point. Once he gets things squared away, there's every chance circumstance will draw him outside the walls of the capital here and there...
Q: What were your inspirations for this novel?
A: The class/skill system is heavily inspired by the one in Rebirth of the Nephilim on this site. I made some changes and took some liberties here and there, but I loved the whole system in that story a lot and based mine off it. If you like Futa and LitRPG, I do recommend that story. Other than that, the main inspiration for my story was wanting to have the sort of LitRPG world where everyone talks in terms of levels, classes, experience, etc. but I've never been the biggest fan of Isekai, so I wanted to write a story that uses the mechanics while being from the POV of people who are from the world. Additionally, I got the idea for the Accords from I own a Brothel in Another World, also on this site though, again, I did my best to change it up to not be simply copying from the other incredibly talented authors on this website. Those are the two main inspirations that come to mind, but I'm sure there are many, many others that influenced me subconsciously or otherwise.
Q: Is there magic for making babies for same sex couples?
A: I haven't fully decided one way or another on this point if I'm being honest, but in a world where the majority of the population is female and a not insignificant number of them are either lesbian or bisexual, I think it would only make sense that someone in the world would dedicate the time to finding such a magic.
"Spoiler Questions":
After some inner debate, I've decided I'll answer some of the questions about the future of the story, but I'll do so somewhat vaguely. I won't give away my plans, but I'll give some hints as to where I'm planning to go.
Q: How big will Zaren's Harem be?
A: Another question I don't have a concrete answer for, but in terms of his inner circle he's met/taken in about half of the girls I originally planned for when I started writing the story.
Q: During the conversation with Fortuna, she talks about Noelle and mentions her lacking any bonds for Allura to work with, does that mean she wasn't one of those women?
A: In short, yes. Allura had nothing to do with Zaren finding Noelle, which means Noelle was never tethered to Allura in any way such as being reincarnated.
Q: There are varying questions about which girls might be reincarnations.
A: I won't give you the who's who just yet, but I will say that not every girl Zaren gets intimate with is one of the reincarnated souls, and not every reincarnated soul will end up in the harem.
Q: Will all reincarnated because of the deal remember their past lives (at least in part)? If they do, how will it be? (Slow or fast, takeover or inheritance?)
A: Allie/Eliya is a special case because of outside interference. The other reincarnated will have an opportunity to regain their past selves if they so choose based on certain conditions. In the event of a reincarnated soul regaining their memories, it will be more of a merger than anything else, it won't erase the person they are now.
Q: Will there be more development with Rolar and Karina?
A: You will be seeing both characters again, have no fear. Both will be involved in the next major arc.